You could pass it as a parameter:
Public Sub Check(valueToCheck as String)
'get the value to here
End Sub
Or create a property on form2 to receive it:
private _HostOrSomething As String = ""
Friend Property HostOrSomething As String
Get
Return _HostOrSomething
End Get
Set(ByVal value As String)
_HostOrSomething = value
End Set
In which case, Sub Check could use _HostOrSomething since it is local var. To use these:
HOST = Test(1)
frm2.Check(HOST)
or
HOST = Test(1)
frm2.HostOrSomething = HOST
frm2.Check